Getting my ASHP set-up right

[kieran]

Hello,

I am just starting a development of 5, 2 bedroom flats in London E8. I've never installed ASHPs before and as a result I'm nervous. I'll happily use enviro-concretes, clay blocks and good standards of insulation but the heating and hot water systems HAVE TO work 365 days a year. When its freezing and someone comes in, these flats have to warm up swiftly and if they want a power shower straightaway then the water must be piping hot.

Part of me says 'Stay with good sized Combi gas boilers', after all until our electricity comes from environmentally sound sources, it's arguably a con to say these are green systems. They use electricity sourced predominantly from gas / nuclear / coal / abroad and that won't change for at least another decade. But okay, if they work I'm up for it.

Each flat is 80sq.m. Each will accommodate 2-3 people. Each flat has 1 bath and 2 showers, a dishwasher and a washer dryer. Insulation will be good; part of the building is new, part is a complete refurb with new windows. I'm keen to keep all the internal equipment to a 600 x 600 x 2400mm cupboard.

One thing that concerns me is comments such as 'when it's heating hot water the central heating stops' and 'they don't work well on really cold days' and 'they're noisy when they're working hard'. I also need to size my systems correctly - what would you advise?

I've come here hoping to be reassured. I want to do this but I just can't afford to get this wrong. The people on this forum seems very knowledgeable but equally no one's saying "I'd install these day-in day-out'...there's always a caveat.

 

I'd really appreciate your advice. Thank you   

[Declan52]

As most people here that have installed them are prepared to put a bit of work in adjusting them to get to work, ask yourself will the people who buy one of your flats do this.

As with everything keep it simple.

[kieran]

1 minute ago, Declan52 said:

As most people here that have installed them are prepared to put a bit of work in adjusting them to get to work, ask yourself will the people who buy one of your flats do this.

As with everything keep it simple.

I shall obviously employ a specialist to set these systems up, but are you saying they need a lot of ongoing management?

[ProDave]

We have an ASHP so I will answer the "concerns"

 

The ASHP needs to be sized to match the  building, if done right it will work properly.

 

A well insulated house will not cool down quickly and only needs a low heat input.  So it does NOT need to heat up quickly.  I estimate if the heating in our house broke down it would be 24 hours before you even noticed.

 

Yes the HP only heats heating OR hot water.  Again if it takes an hour to heat the HW tank you WILL NOT notice that the space heating has gone off for an hour.

 

We live in the Highlands where -10 is common most winters.  The ASHP carries on working.

 

There is no doubt heating a HW tank takes longer so you would just fit a larger tank.

 

They are no more noisy than an oil boiler.  But the noise is outside the house.  Most people are happy to have an oil boiler roaring inside their house, so a similar level of noise outside is not going to bother anyone.

 

An ASHP works best at a low temperature so ideally suited to under floor heating or over sized low temperature radiators.

 

The electricity grid is getting lower carbon all the time as we move away from fossil fuel generation.

 

[Jeremy Harris]

Once set up then they are as simple to control as any other form of electric heating.  All I have for our ASHP is a wall thermostat to set the temperature and a programmer to set when the heating comes on or turns off.  It hasn't needed any fiddling or adjustment since I installed it.

[Ferdinand]

11 hours ago, kieran said:

Hello,

I am just starting a development of 5, 2 bedroom flats in London E8. I've never installed ASHPs before and as a result I'm nervous. I'll happily use enviro-concretes, clay blocks and good standards of insulation but the heating and hot water systems HAVE TO work 365 days a year. When its freezing and someone comes in, these flats have to warm up swiftly and if they want a power shower straightaway then the water must be piping hot.

Part of me says 'Stay with good sized Combi gas boilers', after all until our electricity comes from environmentally sound sources, it's arguably a con to say these are green systems. They use electricity sourced predominantly from gas / nuclear / coal / abroad and that won't change for at least another decade. But okay, if they work I'm up for it.

Each flat is 80sq.m. Each will accommodate 2-3 people. Each flat has 1 bath and 2 showers, a dishwasher and a washer dryer. Insulation will be good; part of the building is new, part is a complete refurb with new windows. I'm keen to keep all the internal equipment to a 600 x 600 x 2400mm cupboard.

One thing that concerns me is comments such as 'when it's heating hot water the central heating stops' and 'they don't work well on really cold days' and 'they're noisy when they're working hard'. I also need to size my systems correctly - what would you advise?

I've come here hoping to be reassured. I want to do this but I just can't afford to get this wrong. The people on this forum seems very knowledgeable but equally no one's saying "I'd install these day-in day-out'...there's always a caveat.

 

I'd really appreciate your advice. Thank you   

 

Have you sorted that you have space to put the ASHPs outside, and where they will go?

[H F]

46 minutes ago, Ferdinand said:

 

Have you sorted that you have space to put the ASHPs outside, and where they will go?

That’s a great point.
 

They will need “breathing space” as the can’t be boxed in. Ours needed a minimum 600mm around the back and sides and nothing blocking it in front so that the cold air could be blown away. 

[kieran]

15 hours ago, Ferdinand said:

 

Have you sorted that you have space to put the ASHPs outside, and where they will go?

Yes. I had been told they could go against a wall though - are you saying I need 600mm all round?

[jack]

5 minutes ago, kieran said:

Yes. I had been told they could go against a wall though - are you saying I need 600mm all round?

 

They definitely need space between them and the wall. Depends on the model - ours is a small one and needed 400mm, from memory

[Roundtuit]

I think ours was a minimum of 200mm behind, 600 in front and 500mm either side to ensure adequate air flow and maintenance access.  Not sure if that would be the same if you have multiple units close together though.

[dpmiller]

it's  one of those RTFM moments...

[kieran]

In fact, 2 of the 5 outside units will be located on their own. I'm then proposing putting 3 units on a flat roof area. Depending on Council approval, the top flat roof is 43 sq metres. If not, a lower one is 15 sq metres so I'm sure I can fit 3 in.

 

I'd be keen to know what size of internal tanks / units people would suggest for a large 2 bed flat and whether a 600x600x2400 cupboard will accommodate all the workings?